One prior method of analyzing large numbers of specimens with a single instrument is with a multiplexed sampling system wherein samples are prepared and supplied to the instrument one at a time. For example, several electrospray needles and a rotating barrier with a hole that allows sprayed fluid streams emerging from the needles to be sampled one at a time has been proposed. Another approach is to provide a gas sampler that sequentially diverts one of a plurality of gas streams to an instrument. One commercially available selector valve performs rapid sample switching between up to 40 sample streams. The problem with either of these multiplexed sampling approaches is that only one specimen is analyzed at a time. To improve the signal-to-noise ratio of the results of the analysis, it is necessary to repeat each sample over and over again.
According to this invention, Hadamard transform or another transform technique is used to analyze multiple specimens simultaneously. This improves the signal-to-noise ratio by a factor of:             (              N        +        1            )        /    2        N          1      /      2      for N separate specimens over the same measurement time or it would reduce the time 4/N to obtain the same signal-to-noise ratio as the individual measurement approach.
The Hadamard transform method is well known in spectroscopy and it is essentially based on solving n simultaneous equations in n unknowns to deconvolute the stored results. Hadamard transform methods have been used in MS/MS experiments in a Fourier transform mass spectrometer as explained by Loh, Williams, McLafferty and Cody in “Simultaneous MS-II Measurements Using Hadamard Transform Fourier Transform Mass Spectrometry”, Analytical Chemistry (1988). In that case, different combinations of precursor ions were selected for dissociation. From the resulting spectra, individual daughter spectra were obtained by solving simultaneous equations. The Hadamard transform method has also been applied to time-of-flight mass analyzers wherein multiple testing conditions are simultaneously used with the same specimen followed by deconvolution with Hadamard transforms as set forth in Franzen U.S. Pat. No. 5,719,392.